This invention relates to pressure sealing devices which are adapted to support an elongated member, or duct, passing through an opening in a partition. While the invention is described herein in relation to its use for protecting the compartment on one side of an aircraft firewall from the transient pressure surges which may occur on the other side of the firewall, it will be readily apparent that the invention may also be used in other applications and environments.
In some jet aircraft, hot air is bled off from the jet engine and is transported by bleed air ducts to other areas of the aircraft for use in the aircraft pneumatic system. The jet engine core is surrounded by a protective firewall which separates it from the nacelle fan duct. The bleed air ducts extend from the jet engine core, pass through the firewall and continue on along the nacelle fan duct into the fuselage. Because space between the firewall and the jet engine is subject to extreme pressures and high temperatures, the firewall is designed to withstand these temperatures and pressures without loss of strength or change in shape. If an unusually high pressure is developed in the region between the engine and the firewall as a result of an engine backfire, for example, the overpressure is relieved by a blow out panel which opens to act as an overpressure fuse by discharging hot gases into the exhaust stream of the engine.
A firewall duct seal is located at the point where each bleed air duct passes from the engine or inner side of the firewall to the outer side to prevent the passage of hot gases and flames from the engine to other parts of the aircraft under normal operating conditions. The duct seal desirably must be able to withstand the temperatures and overpressures to which it is exposed during normal operation of the associated jet engine or engines. Furthermore, the seal must permit the duct to shift because of thermal and vibrational effects.
One aircraft firewall duct seal includes two woven asbestos sheets and a peripheral circular metal spring which is sewn between the sheets. A circular hole is cut from the center of the asbestos sheets inside the area surrounded by the metal spring. The bleed air duct is passed through the hole and the seal is mounted to the firewall over the opening in the firewall. The metal spring encircles the duct and presses the asbestos material against it to effect a seal.
This seal is unsatisfactory in most practical aircraft applications. The spring tends to pinch the asbestos material against the duct, and, in combination with the movement of the duct with respect to the firewall, the asbestos sheets often become chafed. As a consequence, the spring comes in contact with the duct as the asbestos material is worn away. This continued usage causes gouging and abrasive wear of the duct. Most importantly, the integrity of the firewall is eliminated, and there is no seal left to prevent the escape of hot gases through the opening in the firewall. A critical disadvantage of the asbestos seal is its inability to confine overpressure transients to the engine side of the firewall. Additionally, this seal tends to rupture when there is an overpressure or explosion, such as a backfire, on the engine side of the firewall. When ruptured, high temperature engine gases can escape into the fan duct, with concomitant melting and fire damage to the duct. Consequently, the asbestos seal affords unsatisfactory protection from flames and hot gases for the compartment on the outer side of the firewall.
Therefore, it is an object of the invention to provide a rigid partition sealing apparatus which will permit an elongated member to pass through an opening in the partition and maintain the integrity of the partition by preventing flame and hot gases from passing through the opening.
Another object of the invention is to provide an apparatus which will protect an elongated member passing through an opening in a partition from scratches and abrasive wear resulting from movement of the member with respect to the partition.
Another overpressure seal includes a metal collar that is welded to the pipe or duct where it passes through the firewall. However, this seal has the disadvantage of interfering with the installation of the duct through the firewall. Additionally, this seal is unsatisfactory in most practical applications in which the duct is subjected to longitudinal forces or thermally induced length variations because the collar, being welded to the duct, will not allow lengthwise shifting of the duct with respect to the partition once the seal is fixed in position.
Thus, it is another object of the invention to provide a duct seal apparatus that can be easily installed.
A related object to that just stated is to provide a duct seal apparatus which may be readily installed, or removed and reinstalled, solely from one side of the partition, if so desired, where workspace is available on one side of the partition only.
Still another object is to provide a duct seal apparatus for supporting an elongated member where it passes through a partition while allowing lengthwise shifting of the member with respect to the partition.
It is a further object of the invention to provide a duct seal apparatus for supporting an elongated member passing through a partition which will permit shifting of the member with respect to the partition, both orbitally and rotatively.
The term "orbital" as used herein refers to movement of the elongated member such that a point on the the longitudinal axis thereof travels along a path essentially parallel to the face of the partition. It will be recognized that orbital movement of the member could be accompanied by rotative movement thereof with respect to its longitudinal axis and/or lengthwise movement thereof with respect to the partition, as the case may be.